Some people may have an innate green thumb.
I am not one of those people. I am learning as I go. To be fair, I had a little head start, courtesy of my mother's garden, but of course I didn't appreciated it properly at the time.
One thing you have to learn through trial and error is when to follow directions. For example, you can disregard the instructions when you plant bulbs -- if you plant them 6-12 inches apart, as advised on the package, they will just look sparse and sad. However, you do have to follow the directions when you plant vegetables. Seed spacing is important, and seed thinning is even more important. Also, when you build a teepee for your beans and the package says it should be 5-6 feet tall, it really should be 5-6 feet tall. I felt so proud of my orderly little bamboo teepees when I first put them in, but now they're completely overgrown, with beans reaching right past them toward the sky.
Also, fertilizer. Not a very romantic topic, but an important one that came up recently, when my Kristin rose began to falter. I am not a huge rose fan -- generally, I find them too much work -- but Kristin was an exception. This rose bloomed happily all summer. Until this year, when she started succumbing to black spot and mysteriously withering away. My mother-in-law asked me about how often I fertilized the roses, to which I answered something like, "Um? Fertilizer?" I was not entirely ignorant to the importance of nutrients in the soil, but it turns out that I had not been fertilizing nearly enough. After a severe pruning and some careful feeding, Kristin is coming back -- look at those healthy leaves!
Happily, in the spite of these misadventures, most things continue to grow and thrive. Like the Russian sage:
and the begonias: